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[on:]

I have a 16 foot RGB LED strip.  It runs at 12 volts at 14.4 w/m.  I think I understand it needs 144watt power supply at 12v to light them (coming from China, so don't have them in hand yet).  My question is, I'd like to hang these under my RV and have an Arduino do a slow fade through the color spectrum.  The code is easy... coupling the Arduino to a 12v high draw system... well that's why I'm posting.

I've thought about using an optoisolator so the Arduino can pass the PWM signal and 12v on the other side can run the lights...  I just haven't found a chip with 3-4 channels that can drive these LED strips.

I think I've seen an off the shelf item that does this, but they're 23 bucks each.

Ideas?

[Reply #1 on:]

Try to see this:

http://genericnerd.blogspot.com/2009/05/arduino-mood-light-controller.html

I dont know if the ULN2003 can handle the current you need, but there are other darlington arrays that can probably handle more current.

[Reply #2 on:]

I'd love to use the 2003, but it max's out at 500mA and this will pull something like 12A.  I haven't been able to find any array's that can handle more than the 2003.  Some other sites recommended stacking them, but I'd need to stack 24 of them...   something tells me that's not the optimum setup.

I've seen a bunch of systems that can handle the amperage, but don't handle the PWM control.

I found a commercial one for $23.  I may suck it up and grab it... open it up and see how they do it.

[Reply #3 on:]

The 12 A would be about 4A pr. color, so you could probably find a heavy duty transistor and use one pr. color

[Reply #4 on:]

It sounds like you're talking about a FS-SMD5050-12V-DCT-60 with 60 LEDs per meter. It comes in a 16 foot length.

The power requirements are 14.4 w/m (1200 mA/m at 12 volts)

16 feet is 4.9 meters, so that's a total current of 5.9 amps at 12 volts. Any decent MOSFET can switch that. In fact, I think I saw a MOSFET breakout board over at Sparkfun for 4 bucks... http://www.sparkfun.com/products/10256

You were going to use it in your RV... which has a 12 volt supply.

[Reply #5 on:]

I'll check it out.  I've never used a MOSFET.  It will pass the PWM signal?

[Reply #6 on:]

I'll check it out.  I've never used a MOSFET.  It will pass the PWM signal?

Certainly will. Just be sure it's a logic level mosfet (as that sparkfun module uses) as a standard mosfet will not turn on fully with a arduino +5vdc digital output. SparkFun also sells just the mosfet alone for around $1.

Lefty

[Reply #7 on:]

Awesome.  Just ordered the breakout and a few extra. 

At what point should they run with a heat sink?

[Reply #8 on:]

Awesome.  Just ordered the breakout and a few extra. 

At what point should they run with a heat sink?

As that mosfet has a Ron value of .047 ohms when turned on I would think anything under 5 amps or so ( = 1 watt heat dissapation) would be fine. Much more of course with a heat sink.

Lefty

[Reply #9 on:]

There are MOSFETs with Ron of 0.004 ohms or so which will take 12A without much heatsinking needed - a bit more expensive though.  You _must_ make sure its a logic-level MOSFET though (in the datasheet the Ron will be specified for Vgs=4.5V if its a logic level device).